I have to watch my intake of copper, and take 2 supplements to keep it in check. I have been advised to avoid Shellfish, Peanuts, Cashews and other copper-heavy foods. I don't use copper utensils for food. I recently tossed out my water kettle because I realized it has a copper bottom!
Every 3 -5 months I have a Ceruloplasmin blood test to check my copper level. Why? you may ask. Well, here are two sources with a little more information, and links to the full articles.

1. The Role of Copper in the Angiogenesis Process - from: cancerprotocol.com

Copper is believed to be the switch that turns on the angiogenesis process in tumor cells. It has been observed that abnormally high serum copper levels are found in patients with many types of progressive tumors.

According to the University of Michigan Oncology Journal, many studies have shown copper to be an obligatory co-factor in the process of angiogenesis. Growth factors in angiogenesis require binding to copper in order to function properly. As stated in Steven Brem's research at the Moffitt Cancer Center, linked below, "copper-binding molecules [ceruloplasmin, heparin, and tripeptide glycly-histadyl-lysine] are non-angiogenic when free of copper, but they become angiogenic when bound to copper."

On January 21, 2000, the University of Michigan reported that researchers had "successfully stopped the growth and spread of cancer by depriving the tumors of the copper supply they need to form new blood vessels." Dr. George Brewer used an inexpensive compound called tetrathiomolybdate (TM) to lower the serum copper levels in patients with cancer.

This study was done with a group of 18 patients in hospice with 11 different types of metastatic cancer. The goal of the study was to reduce ceruloplasmin to 20% of baseline for at least 90 days. The treatment achieved this goal in 6 patients, and 5 of those patients have seen no tumor growth or new tumors for more than 2 years. The other 12 patients could not achieve the target copper levels, suggesting that it can take more than a month to reduce copper levels to target, during which time the cancer may progress rapidly." - Read full article here.

2. What is the evidence? - from : http://www.cancer.org

Copper is a trace mineral that is needed for many important body processes. Animal studies have shown that copper is useful in maintaining antioxidant defenses. Antioxidants block the actions of free radicals, which are activated oxygen molecules that can damage cells. While the role of copper in the cancer process is still unclear, copper complexes have been shown to have anti-cancer properties in laboratory studies.

Other laboratory and animal studies suggest that high copper levels may be linked to liver cancer and brain tumors. More recently, many studies have shown that patients' blood copper levels are higher in several types of cancer and other diseases. To add to the confusion, blood tests can show high copper levels even when there is little copper in the tissues. These high copper levels may be due to injury, disease, or inflammation. Because copper levels in the blood do not always reflect nutritional status, it's hard to design or find good studies of copper.

Copper is needed to form new blood vessels, and because cancer needs new blood vessels in order to grow, some researchers are lowering copper levels to see if it will help slow tumor growth. In effect the researchers are trying to use low copper levels to starve the tumor of nutrients by keeping it from building new blood vessels (anti-angiogenesis). One group of researchers looked at whether a copper-lowering drug, tetrathiomolybdate (or TM), could help patients with advanced kidney cancer. Some patients' cancer stopped growing during the 6-month treatment period. A few people had low white blood counts during treatment, requiring that treatment be stopped until they recovered. This was a small study, and further research is needed to find out whether copper can help more people with advanced cancer - Read the full article here.